The gastroenterology service has been involved with intestinal and hepatic aspects of marrow transplantation for 10 years, providing clinical consultation, performing diagnostic and therapeutic procedures and carrying out clinical research in close collaboration with pathology (Project X.C), virology (Project III), and nutrition (Project X.D.). Consultations involve pre-transplant intestinal problems and a wide range of post-transplant disorders related to chemoradiation toxicity, acute GVHD, enteric and liver infections, side effects of medication, and chronic GVHD. Procedures include upper intestinal endoscopy, mucosal biopsies, coagulation of bleeding sites, esophageal dilation, colonoscopy, percutaneous liver biopsy, and esophageal manometry. Research projects included in this section are studies of hepatic venocclusive disease, intestinal GVHD, and hepatic viral infection. We will analyze the incidence of venocclusive disease (VOD) of the liver and the risk factors associated with this complication. We will conduct a randomized trial of continuous infusion of heparin for the prophylaxis of VOD. We will examine intestinal epithelial cell proliferation in patients with acute GVHD, testing the hypothesis that GVHD damages progenitor crypt cells. We will use immunohistologic methods and electron microscopy to identify a subset of intestinal intraepithelial lymphocytes which may be involved with alloimmune crypt cell destruction in patients with acute GVHD. We will study the relationship of viral infections of the liver and manifestation of GVHD In a prospective study of patients with posttransplant liver dysfunction. An ongoing study of intestinal carbohydrate absorption after transplantation will be continued with emphasis on recovery of intestinal disaccharidase activity following acute intestinal GVHD. These collaborative studies are all carried out in human marrow transplant recipients, with both clinical and research data emanating from consultations and procedures by the gastroenterology section.